Trailblazer of the Week

Yiyi Cai

31 March 2023

From a young age, Yiyi Cai’s grandfather would often give her fun logic puzzles to solve in the hopes that she would one day become a mathematician. Today, those puzzles look more like the proofs and theory-based applications of computer programming.

“I was always encouraged to become who I want to be,” says Cai, a Caltech sophomore and Mission Operation Systems and Ground Data Systems (MOS/GDS) intern for the Lunar Trailblazer mission. “The sense of fearlessness my family instilled in me drives me to, as the old saying goes, either find a way or make one.”

One initial obstacle Cai faced after she immigrated from China to California six years ago was when she began attending high school and couldn’t really speak any English.

“It was the belief that I was more than how others defined me that motivated me to get out of my comfort zone, become fluent in English, take as many additional classes as possible to catch up with my peers, and challenge myself whenever I could,” she says.

And discovering computer programming made that all the more possible.

“My first-ever computer science class in high school was deeply inspiring to me,” recalls Cai. “I remember sitting in the classroom, barely understanding any English while struggling to follow the instructions to type out the simplest program possible. The moment the two words “Hello World” showed up on the screen, however, a new world opened up to me—one that disregarded differences of language, gender, ethnicity, and wealth. The world of coding had a universal language and simple objective goal. The singular measure of success was code functionality and—as luck would have it—my coding skills proved excellent.”

That they did. Cai became the co-captain of her high school’s Science Olympiad team, she wrote an introductory Python coding textbook for kids, and she participated in a couple of research programs where she applied her new programming skills to analyze data in other fields, including psychology and volcanology.

“I was beyond shocked that my coding skills were immensely useful in even analyzing volcanoes!” she says.

Now as a Caltech student majoring in Electrical Engineering and minoring in Computer Science, Cai has switched gears from computational coding to the theoretical nature of programming. Combining her love of physics and computer science, she’ll be participating in Caltech’s Summer Undergraduate Research Fellowships (SURF) program this summer to assist Prof. John Preskill in error cancellation of quantum simulators.

“I am very excited to try out a different side of research,” she says.

What’s more, she’s currently working as an admissions ambassador giving tours to prospective students, helps run the social media for Caltech’s ultimate frisbee team, and—lest we forget—works part-time as a Lunar Trailblazer MOS/GDS intern.

“During my first-year orientation at Caltech, Professor Bethany Ehlmann presented the Lunar Trailblazer mission to us,” says Cai. "I was fascinated by the fact that a space mission was accessible to me as a Caltech student. I didn’t think I would be offered the opportunity because I didn’t have any background in space missions before, but I decided to give it a shot, just in case something miraculous happened—and it did! It still feels surreal to have been hired as a first-year student who only had stepped on campus two months before the talk was given!”

To perform as an MOS/GDS intern, Cai first had to familiarize herself with Trailblazer’s relevant coding libraries and interfaces used for its command systems.

“The most challenging part of my role was to get started with the task,” says Cai. “Oftentimes I would have a lot of questions—how would this specific script help with the specific goal we want to achieve? It was also intimidating to work with a group of experts in their fields as a first-year college student, but everyone has been so patient and welcoming.”

Now that she’s well-versed, Cai has written scripts to support Trailblazer’s remote transmission, or telemetry, of acquired data throughout its lunar orbital mission.

“I primarily process and analyze command data using various Python coding scripts,” she says. “More specifically, I wrote scripts that verify the validity of commands sent to the spacecraft and process telemetry data sent by the spacecraft once it’s launched. These scripts are important in identifying imprecise commands and ensure that the spacecraft travels as intended in space.”

Besides coding such vital fault protections, Cai enjoys figure skating, hiking, reading romcoms, and “taking pictures of the wonderful people and things around her.” She has also been exploring ways to apply her skills for social impact.

“I have created a rhetorical device identifier app in the hopes of helping English learners who might share the same struggles as I did when I first learned it,” she explains.

But Cai also asserts the importance of individuality and how attempting full assimilation isn’t the ultimate goal.

“As part of an underrepresented group in STEM, I often felt out of place, and the sense of belonging was difficult to establish,” says Cai. “The logic usually goes: because I’m not the same as everyone else in the field, I’m not as good and should try to make myself as similar to them as possible. However, it is crucial to recognize that it is your uniqueness that brings valuable perspectives to the table. Don’t be afraid to speak out!”

For Cai, the Lunar Trailblazer team manifests this power.

“It’s fascinating to see how the Trailblazer community from all around the world works on different aspects of the mission and collaborates together!” she says. “I feel so honored to be part of this mission, and the scientific research that constantly pushes our understanding of the world forward never ceases to amaze me.”

To some, the Universe can only be explained by numbers alone: equations, magnitudes of meaning, and hierarchies. But to Cai, when it comes to charting her path, nothing is fixed.

“The competitive educational system that I grew up in—where class rank started in first grade— often made me feel lost about how I was valued as a human being,” says Cai. “That’s when I turned to the sky—the vastness of mystery. Growing up I always wondered what’s actually out there. Never in my life would I have imagined that I would be working on a mission sent to space!”

Yiyi Cai is a Caltech MOS/GDS intern and Trailblazer of the Week!

Trailblazer of the Week is an ongoing series showcasing the diversity of experience and expertise that supports the collective determination of the Lunar Trailblazer mission.

By Emily Felder
Emily Felder is a Pasadena City College student and Caltech intern working on science communication for the Lunar Trailblazer mission.